Conventional buckle tensioners for a vehicle comprise a linear drive, which is connected with a belt buckle via a traction member, and a deflection member adapted to deflect the direction of the traction member between its end connected with the belt buckle and its end connected with the linear drive.
Such a buckle tensioner serves to take up the so-called slack in a safety belt system shortly before an accident impact so that the safety belt is applied as tightly as is expedient to a vehicle occupant wearing a seat belt and such occupant may participate in the deceleration of the vehicle from an early point in time. To take up such belt slack in a buckle tensioner arrangement the belt buckle is moved away from the vehicle-fixed anchoring points of the safety belt, for example toward the vehicle's floor. The displacement of the belt buckle may be produced using a linear drive which generally comprises a cylinder tube and a piston able to move in translation therein. The cylinder tube is provided with a propellant charge which, after ignition as caused by a suitable triggering system, produces gas under pressure, which in turn displaces the piston in the interior of the cylinder tube. Such displacement is transmitted by the traction member to the belt buckle.